In 1911, the Irrigation Investigations Unit (IIU) of the U.S. Department of Agriculture was established in Fort Collins in conjunction with Colorado Agricultural College (now Colorado State University). Scientists within the unit studied and designed apparatuses to measure water flow through canals and diversion structures, investigated various irrigation projects, and conducted snow surveys. The Irrigation Research Papers collection includes letters, data, field books, drafts, reports, blueprints, maps, conference materials, photographs, and negatives. For more information see the finding aid.

This digital collection, with materials dated 1903 to 1956, includes more than 3,100 images as well as correspondence, data, reports, and conference materials generated by IIU staff during their investigations.